As-yet-unpublished Canadian data raises concerns about whether it's a good idea to get a seasonal flu shot.

A series of studies suggests that people who got a seasonal flu shot last year are about twice as likely to catch swine flu as people who didn't.

Journals bar would-be authors from discussing their results publicly before they go through peer review, but the findings have been a poorly kept secret and many in the public health community in Canada have heard about them.

Even unpublished, the paper has convinced several provincial health agencies to announce suspensions of seasonal flu vaccinations. Quebec, Alberta, Saskatchewan, Ontario and Nova Scotia have suspended seasonal flu shots for anyone under 65 years of age.